Ice removing covering for airfoils



March 30, 1948. R. G. CAMPBELL IICE REMOVING COVERING FOR AIRFOILS FiledMarch 17, 1944 2 sheets-sheet 1 MarCh 30, 1.948.- R Q CAMPBELL ICEREMOVING COVERING FOR AIRFOIL 2 shets-sneet z Filed March 17, 1944Patented Mar. 30, 1948 UNITED STATES TENT OFFICE ICE REMOVING COVERINGFOR AIRFOILS Application March 17, 1944, Serial No. 526,866

6 Claims. 1

` This invention relates to protective coverings or apparatus forairfoil-s and especially to inflatable coverings for preventing theaccumulation of ice on the leading edge of such airfoils.

Objects of the invention are to provide effectively for breaking andremoving ice formations on the leading edge of an airfoil; to providefor moving laterally pieces of broken ice into the ambient airstream forremoval by the latter; to provide for expanding a protective covering orapparatus along an element thereof extending diagonally across theleading edge; to provide for local expansion of such diagonal element;to provide for expanding a central zone of the covering along one ormore sinuous paths extending span- Wise along and across the chord lineof the leading edge; and to provide simplicity of construction,convenience of manufacture and effectiveness of operation.

These and other objects and advantages of .the invention Will beapparent from the following description.

In the accompanying drawings which form a part of this specification andin which like numerals are employed to designate like parts throughoutthe same,

Fig. 1 is a perspective View of protective apparatus having a pluralityof sinuous inflatable tubes installed on the leading edge of an airfoil,parts being broken away and in section,

Fig. 2 is a plan view from above of a modified construction of theprotective covering shown in Fig. 1, before mounting on the airfoil,parts being broken away,

Fig. 3 is a view like Fig. 2 showing another modication of theprotective covering, and

Fig. 4 is a perspective plan View from above of a further modificationof the protective covering, parts being broken away and in section.

In an embodiment of the invention illustrated in Fig. 1 a protectiveapparatus I!) includes a body or covering I I of resilient rubber orother rubberlike material mounted at the leading edge of an airfoil I2such, for example, as a wing of an aircraft. The covering I isconstructed and arranged to provide a substantially smooth aerodynamiccontour around the leading edge for maintaining the aerodynamiccharacteristics of the airfoil. The body II may be adhered throughoutthe extent of its inner surface I3 to the skin of the airfoil I2 or maybe attached in a suitable manner as by screw fasteners (not shown) atits upper and lower attaching margins I4 and I5, respectively. For thelatter arrangement of attachment, the covering is mounted in a conditionof stretch between the margins I4, I5 to hold the covering against theairfoil when not in operation.

The rubber body or covering II has embedded therein a pair of adjacentinflatable tubes or elements It and I'I curved uniformly about the chordline I3 of the leading edge and 180 out of phase relative to each other,the tubes having walls of suitable resilient rubber-like material. Thetubes are arranged in an overlapping manner and each extends spanwise ina sinuously curved path along the leading edge and across the chord lineI8, the tubes i t, Il being in overlying relation at spacedapart regionswhere they diagonally cross the chord line.

It is desirable that the inflatable tubes I6, I'I be disposed adjacentthe outer surface of the covering iI and have walls of considerablestretchability. Such walls may include in the rubber thereof reinforcingmaterial such as stockinette or other knitted or otherwise stretchablefabric, preferably of nylon or rayon, although cotton or other suitablematerial may be used. The stookinette fabric is stretchable bothcircumferentially and longitudinally of the tube, which permitsextensive stretching of the tube Wall for expanding the cover locally atthe tube zone to break and loosen the ice thereon for removal by theambient airstream. However, the reinforcing material in the walls of thetubes I6, I'I may, if

desired, be of substantially inextensible material such, for example, assquare-woven, straight-laid fabric for imparting stretching force toadjacent rearward portions of the covering I0 upon inflation thereof.

The inflatable tubes I6, I1 have curved portions or reaches 2|, 22 and23, 24 extending diagonally back and forth across the chord line of theleading edge, and have their adjacent margins at separated positions asat 25, 26, and 21, 28 and p i loosen such particles for their removal bythe ,airstream.

The fabric and rubber part-s of the covering are united by vulcanizationand heat under pressure. In the operation of the protective coveringIII,

when such covering is provided with inflatable tubes IS, li havinghighly stretchable walls, the two tubes may be inated in a cyclicalmanner individually or simultaneously and may be inated through suitableconnector and conduit means in communication with such tubes at one endthereof and with a suitable source of air under pressure which may belocated within the body of the aircraft, for example. These tubes thendistend outwardly to a substantially semicircular shape in cross-sectionas shown by broken lines at 3l and 32 in Fig. 1, the Walls 4of suchtubes stretching locally to a relatively greatextent within themselvesby virtue of the stretchable action of the nylon fabric. Opposite loopportions 341, 3-5, 3 and 3l of these sinuous tubes at the regions `ofreverse curvature tend, upon ination, to spread apart due to thecurvature of the leading edge, which spreading acti-on coacts with thecracking action of the tubes at the diagonally extending curved portions2l, 22, 23 and 26 to provide the desired lateral movement of the brokenice formation along the latter portions for its removal by the. ambientairstream. When the tube l5, for example, is inated, the central tubezone 20 is expanded along the sinuous path of such tube back and forthacross the chord line of the leading edge and the outer portion of therubber body ll overlyingr such tube I 5 is stretched extensively withlittle or no stretching force Vupon theV adjacent portions rearwardly ofthis tube le.; A similar stretching and expanding action occurs uponv`inflation of the sinuous tube Il; The local stretching of these tubesI6,

Y Il is found to be highly effective, especially at the immediateleadingedge region, in cracking and loosening the ice formation, which crackingoccurs in reaches; diagonally of the chord line of the leading edgerather than parallel thereto. Parts ofthe broken iceare moved laterallyrelative to and about the chord line for action thereonby the ambientairstream. In this manner Vsuch ice formationupon the covering isremoved promptly and thoroughlyLespecially throughout the extent of thecentral tube zone 2o.

4'/Vhen the protective covering IU is `provided with inflatable tubesit, il having walls of substantially inextensibl'e fabric, the coveringis mounted in `a condition` of stretch l'mtweenv attaching margins Id',I 't5 a'svdescribed hereinabove, and the tubes IB', lima-y be inated inav cyclical manner individually or simultaneously. `By virtue of therelatively inextensible walls-of the tubesY l', l'l, these tube-s, wheninflated, distend outwardly and assume an expanded condition havingAlesser sharpness ofcurvature than that of the semi-circular shapeobtained when the tubes have Walls of highly stret-chable fabric. Uponinflation of such tubes; they expand the covering at the central A'tubezone 2e, cracking the` ice for,-

niation thereon in reaches diagonally of .the chord lineof the leadingedge and alongl the sinuous paths back and forth across such cho-rdline, and moving portions of the ice laterally relative to the chordline forremoval bythe iiow of, air. VThis action ,isV also effective inimparting stretching forceY to and moving outwardly from the airfoil theadjacentrearward portions ofthe covering ,lo to break and loosen the iceformations 'on the, latter portions. In this manner the covering is,expanded along overlapping sinuous paths spanwise throughout the centralzone 2Q, and the rearward portions adjacent theY tubes are stretched asubstantial. extent whereby :the 'ice formati-ons thereon` are crackedand broken for the thorough and prompt removal of such ice by the now ofair across the covering.

The modied construction `of the protective covering di! of suitableresilient rubber-like material is constructed and arranged in a mannersimilar to that of the protective covering It except that a single tube4| is disposed in a sinuous path extendingrspanwise back and forthacross the chord line i8 -of the leading edge, which tube l may beinflated by a suitable conduit and connector means 12in communicationtherewith at an end of the protective covering. The rubber walls of thetube!!! may include reinforcing material of substantially inextensiblefabric for stretching rearward portions of the covering 4Q or'mayinclude highly stretchable fabric like nylon stockinette fabric thereinfor local stretching of the covering along the sinuous path of the tube.For the arrangement shown in Fig. 2, the tube El' is not continuouslycurved relative to theY chord line I8 but comprises substantiallystraight portionsV or Lreaches 43,114, 45 extending diagonally acrossthe chord line and at an angle of inclination with respect to such chordline I8, adjacent straight portions 43, 44 beingopposingly inclinedrelativel to each other. TheV chordwise extent of the covering includedwithin the central tubezone is such as to make possible the desiredtwisting and lateral shifting movement diagonalli7 acrossv the chordline I8' of partsof the ice formation upon the-breakingand crackingthereof due to the inflation of tube 4I thereby facilitating the action`of the ambient air-stream in further loosening and removing the'brokenpieces of' ice. The operation ofthe covering 40, when installed onthe'leadn'g edge ofthe airf'oil, is substantially as describedhereinabove-for the covering l0.

l'f desired, two of Fig. 2 may be arranged together in 130"phaserelationship orrin other desired relationships'.

For the modiedconstruction ofthe protective covering 5B of suitableresilient rubber-like'mate- Y rial shown in Fig. 3, one or more tubes5l', 52 exa sinuous path may be provided yandmay be in- Vlated bysuitable conduit and .connector means 53 `in communication therewith.These't'ubes 5l, 52 are embedded' in the rubberv body of the. protectivecovering in the manner, described hereinabove for the protectiveVcovering it and the rub-'- ber walls thereof may include reinforcingmaterial of suitable substantially inextensible fabric or of suitablehighly stretchable fabric. The tube 5I has straight portionsV or reaches54', 54 extendingV diagonally across the chordk line VI3 and at an angleof inclination relative to such chord line, and includes straightportions 55, 55 extending chordwise substantially normal to the chordline I8, adjacent inclined portions and adjacent normal portions beinggenerally parallel.

rIhe provision of two gtubes as in the embodiment of Fig. 3 makespossible various phase relan tionships, as desired. For example, the twotubes maybe arranged in phase, 90`V or 180 out of phase, or in otherdesired arrangements, and one tube may be in the same'fo'rmation vas theother or more tubes of theformation sinuous path of the tube, and alongthe inclined straight portions 54, 54 the cracked ice isshiftedlaterally by virtue of inflation of such tube 5I as describedhereinabove for the covering I0.

In the embodiment of Fig. 4, a protective covering 60 of suitableresilient rubber-like material includes inflatable tubes 6I, 62 disposedin the central tube zone 63 between attaching margins 64 and 65 andincludes stretchable portions 66 and 6l extending rearwardly from thecentral zone 63, such stretchable portions having spacedapart apertures10, 'l0 extending therethrough for venting the covering 60. Theattaching margins 64 and 65 include therein reinforcing strips 68, 66 ofsuitable relatively inextensible fabric material folded about metalIbead elements 69, 69.

The covering 60 is mounted on the airfoil in a condition of stretchbetween the attaching margins 64 and 65 as by suitable screw fasteners(not shown) extending through the rubber material and the reinforcingstrips 68, 68 inwardly of the bead elements 69, 69. An offsetarrangement is provided for mounting a fairing strip (not shown) forfacilitating smooth flow of air across the covering at such margins.

Theinatable tube 62 having a wall of suitable resilient rubber-likematerial includes in such Wall expansion-limiting reinforcement ofsuitable substantially inextensible fabric material and such tube isembedded in the rubber covering 60 desirably adjacent the inner surfacethereof. The tube 62 is disposed centrally about the chord line I8 andextends in a straight path along such chord line. When the tube 62 isiniiated and distended outwardly, it assumes a generally rounded form insection which action moves the stretchable portions 66 and 61 outwardlyfrom the airfoil and imparts stretching force to the portions 66, 61,effectively breaking and loosening the ice thereon for thorough andprompt removal by the flow of air over the covermg.

The tube 6I has a Wall of suitable resilient rubber-like material andincludes therein highly stretchable nylon stockinette fabric. The tube6l may be superimposed upon the tube 62 adjacent the outer surface ofthe covering 60. Such tube 6| extends along the central tube zone 63 ina sinuously curved path back and forth diagonally across the chord lineI8 of the leading edge. As described hereinabove for the covering I6,when the tube 6| is inflated, the protective covering 6D is expandedlocally at the central zone 63 along the sinuous path of such tube 6Ibreaking and loosening the ice formation along the latter tube andproviding the desired lateral shifting movement of the broken pieces ofice into the path of the ambient airstream whereby such pieces arethoroughly and promptly removed.

lln the operation of the covering 60 the inflatable tube 6I is inflatedfirst for locally expanding such covering at the central zone andfacilitating the effective removal of the ice formation immediately atthe leading edge along the chord line I8. The tube 6I is then deflatedand the tube 62 is next inflated, which action further promotes removalof any remaining pieces of ice at the central zone 63 and stretching thestretchable portions 66, 61 for cracking and breaking the ice formationthereon for removal by the ambient airstream. If desired, the twosuperimposed tubes 6I, 62 maybe inflated simultaneously.

. ratus comprising a covering for said leading edge comprising resilientrubber-like material having an inflatable tube extending along thecovering and throughout the width of its bore diagonally across asubst-antially straight line along the covering with a portion of saidtube throughout the width of its bore disposed entirely to one side ofand spaced from said line and with another portion of said tubethroughout the width of its bore disposed entirely to the other side ofand spaced from said line, said covering being constructed and arrangedto present upon ination of said tube a distended surface of the coveringsubstantially coextensive with the Width of said tube throughout itsextent.

2. Apparatus for preventing the accumulation of ice on the leading edgeof an airfoil, said apparatus comprising a covering for said leadingedge comprising resilient rubber-like material having an inflatable tubeextending in a sinuous path along the covering crossing and recrossing asubstantially straight line along the covering at spaced-apart positionsalong said line with portions of the tube throughout the width of itsbore disposed entirely to one side of and spaced from said line and withother portions of the tube throughout the width of its bore disposedentirely to the other side oi and spaced from said line, said coveringbeing constructed and arranged to present upon inflation of said tube adistended surf-ace of the covering substantially coextensive with thewidth of said tube throughout its extent.

3. Apparatus for preventing the accumulation of ice on the leading edgeof an airfoil, said apparatus comprising a covering for said leadingedge comprising resilient rubber-like material having an inflatableItube including stretchable fabric material in the wall thereof forlocal stretching of said covering and extending in a sinuous pathspanwise along the covering crossing and recrossing =a substantiallystraight spanwise-extending line of the covering at lspaced-apartpositions along said line with portions of the tube throughout the widthof its bore disposed entirely to one side of and spaced from said lineand with other portions of the -tube throughout the width of its boredisposed entirely to the other side of and spaced from said line, saidcovering being constructed and arranged to present upon ination of saidtube a distended surf-ace of the covering substantially coextensive withthe width of said 'tube throughout its extent.

4. Apparatus for preventing the accumulation of ice on the leading edgeof an airfoil, said appa- Iratus comprising a covering for said leadingedge comprising resilient rubber-like material having a plurality ofinflatable tubes in superimposed relation to one another extending alongthe covering, at least one of said tubes extending in a sinuous pathalong the covering crossing and recrossing a substantially straight linealong the covering at spaced-apart positions along said line inoverlapping relation with another of said tubes to the other side of andspaced vfrom said 1ine,-

said covering being constructed and varranged to present upon inaitionof said` sinuous tube Va distended surface of the coveringlsubstantially coextensive with the width of such tube thro-ughouti'tsextent. y

5. Apparatus for preventing the accumulation of ice ori-the leading edgevof an airfoil, said apparatus comprising a covering Vfor said leadingedge comprising resilient rubber-like'material having a pair 'iniiatable`tuloesin superimposed relation to one another each extending in asinuous path along the covering crossing and reerossing a substantiallystraight'line along the covering atspaced-,apart positions along saidlinein overlapping relation With-,the other v tube at saidpositions,vthe portions of said pairof inflatable tubes between the crossingpositions being disposed on opposite sides of and spaced from said line,and said covering being `constructed and arranged to present uponinflation ofv each inatable tube a distended surface of the coveringsubstantially coextensive :with -thewidth of the l'tube throughoutitsextent. Y Y

ii. Apparatus for preventing the accumulation o f ice on the leadingedge, said apparatus com-` @rising aycovering for sai'dleading edgecompris` ingV resilient rubber-like material lhaving va pair ofinatabl-e tubes -in superimposed relation to one another "each extending4in a 4substani'fially continuously curved sinuous path spanWise alongthe coveringy crossing and recrossing a substantially straight spanwise-extending 'lneatgspacedapart position's'along -said 'line vinoverlapping relation with the other tube at said positions, the portionsof said pair Ao .f inatable tubes vbe-` tween the crossing Apositionsbeing disposed on opposite sides of and spaced -from said line, and eachYofthe inflatable tubes including stretchable fabric material in theWall thereof lfor local distentionof the covering upon -ination of thetubes to present a curved surface yof the covering lsubstantiallycoextensive with the Width of the tube throughout its extent. c

' ROBERT CAMPBELL.

Number Name j "Date 2,025,919 wane V V nec. 31', 1935 2,251,430 TaylorAllg. 5, 1941 2,327,034 Geer I7, 1943 c

